Polyacrylamides are being used in increasing quantities in enhanced oil recovery (EOR).
Large facilities for dissolving polyacrylamides have treated tens of kilograms per hour until recently. The problem of initially wetting the powder, which tends to agglomerate a great deal, has been solved using simple methods (ejectors, wetting shovels, nozzles within a tube, etc.). These methods facilitate low flow rates at low concentrations (0.5%) and long dissolving times (1 hour for standard powders with a particle size less than 1 mm).
The document WO 2011/107683 describes a device (PSU or Polymer Slicing Unit) that both grinds and disperses the powder in the dissolving water (solution water). This apparatus is composed of a rotor with sharp blades and a stator with thin slots. Depending on the thickness of these slots, the powder is more or less ground finely. Dissolving is almost instantaneous with slots of 200μ but the flow rate is low. Slots of approximately 700 microns reduce the dissolving time to 30 minutes and obtain very high concentrations in the order of 20 gr/liter. These concentrations greatly reduce the size of the dissolving tanks and metering pumps which has the advantage of a significant reduction in the corresponding financial investment.
The stator of this apparatus has slots that are cut by a fine jet of very high-pressure water (200 MPa (2000 bar)) or by using a laser.
The disadvantage of this type of stator is that it gives rise to vibrations inside the apparatus that lead to premature bearing wear. This wear has consequences for the functioning of the apparatus and the ability thereof to dissolve large quantities of polymer.